diff options
Diffstat (limited to 'OldMdePkg/Library/BaseLib/Ia32/Thunk16.S')
| -rw-r--r-- | OldMdePkg/Library/BaseLib/Ia32/Thunk16.S | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/OldMdePkg/Library/BaseLib/Ia32/Thunk16.S b/OldMdePkg/Library/BaseLib/Ia32/Thunk16.S new file mode 100644 index 0000000000..c45cdb0a2d --- /dev/null +++ b/OldMdePkg/Library/BaseLib/Ia32/Thunk16.S @@ -0,0 +1,200 @@ +#------------------------------------------------------------------------------
+#
+# Copyright (c) 2006, Intel Corporation
+# All rights reserved. This program and the accompanying materials
+# are licensed and made available under the terms and conditions of the BSD License
+# which accompanies this distribution. The full text of the license may be found at
+# http://opensource.org/licenses/bsd-license.php
+#
+# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+#
+# Module Name:
+#
+# Thunk16.S
+#
+# Abstract:
+#
+# Real mode thunk
+#
+#------------------------------------------------------------------------------
+
+.globl ASM_PFX(m16Start), ASM_PFX(m16Size), ASM_PFX(mThunk16Attr), ASM_PFX(m16Gdt), ASM_PFX(m16GdtrBase), ASM_PFX(mTransition)
+.globl ASM_PFX(InternalAsmThunk16)
+
+ASM_PFX(m16Start):
+
+SavedGdt: .space 6
+
+ASM_PFX(BackFromUserCode):
+ push %ss
+ push %cs
+ .byte 0x66
+ call L_Base1 # push eip
+L_Base1:
+ pushfw # pushfd actually
+ cli # disable interrupts
+ push %gs
+ push %fs
+ push %es
+ push %ds
+ pushaw # pushad actually
+ .byte 0x66, 0xba # mov edx, imm32
+ASM_PFX(ThunkAttr): .space 4
+ testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15, %dl
+ jz 1f
+ movl $0x15cd2401, %eax # mov ax, 2401h & int 15h
+ cli # disable interrupts
+ jnc 2f
+1:
+ testb $THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL, %dl
+ jz 2f
+ inb $0x92, %al
+ orb $2, %al
+ outb %al, $0x92 # deactivate A20M#
+2:
+ movl %ss, %eax
+ .byte 0x67, 0x66, 0x8d, 0x6c, 0x24, 0x34, 0x66
+ mov %ebp, 0xffffffd8(%esi)
+ mov 0xfffffff8(%esi), %ebx
+ shlw $4, %ax # shl eax, 4
+ addw %ax, %bp # add ebp, eax
+ .byte 0x66, 0xb8 # mov eax, imm32
+SavedCr4: .space 4
+ movl %eax, %cr4
+ lgdtw %cs:0xfffffff2(%edi)
+ .byte 0x66, 0xb8 # mov eax, imm32
+SavedCr0: .space 4
+ movl %eax, %cr0
+ .byte 0xb8 # mov ax, imm16
+SavedSs: .space 2
+ movl %eax, %ss
+ .byte 0x66, 0xbc # mov esp, imm32
+SavedEsp: .space 4
+ .byte 0x66
+ lret # return to protected mode
+
+_EntryPoint: .long ASM_PFX(ToUserCode) - ASM_PFX(m16Start)
+ .word 0x8
+_16Idtr: .word 0x3ff
+ .long 0
+_16Gdtr: .word GdtEnd - _NullSegDesc - 1
+_16GdtrBase: .long _NullSegDesc
+
+ASM_PFX(ToUserCode):
+ movl %ss, %edx
+ movl %ecx, %ss # set new segment selectors
+ movl %ecx, %ds
+ movl %ecx, %es
+ movl %ecx, %fs
+ movl %ecx, %gs
+ movl %eax, %cr0
+ movl %ebp, %cr4 # real mode starts at next instruction
+ movl %esi, %ss # set up 16-bit stack segment
+ xchgw %bx, %sp # set up 16-bit stack pointer
+ .byte 0x66
+ call L_Base # push eip
+L_Base:
+ popw %bp # ebp <- offset L_Base
+ addr16 pushl 36(%si)
+ .byte 0x36
+ lea 0xc(%esi), %eax
+ push %eax
+ lret
+
+L_RealMode:
+ mov %edx, %cs:0xffffffc5(%esi)
+ mov %bx, %cs:0xffffffcb(%esi)
+ lidtw %cs:0xffffffd7(%esi)
+ popaw # popad actually
+ pop %ds
+ pop %es
+ pop %fs
+ pop %gs
+ popfw # popfd
+ lretw # transfer control to user code
+
+_NullSegDesc: .quad 0
+_16CsDesc:
+ .word -1
+ .word 0
+ .byte 0
+ .byte 0x9b
+ .byte 0x8f # 16-bit segment, 4GB limit
+ .byte 0
+_16DsDesc:
+ .word -1
+ .word 0
+ .byte 0
+ .byte 0x93
+ .byte 0x8f # 16-bit segment, 4GB limit
+ .byte 0
+GdtEnd:
+
+#
+# @param RegSet Pointer to a IA32_DWORD_REGS structure
+# @param Transition Pointer to the transition code
+# @return The address of the 16-bit stack after returning from user code
+#
+ASM_PFX(InternalAsmThunk16):
+ push %ebp
+ push %ebx
+ push %esi
+ push %edi
+ push %ds
+ push %es
+ push %fs
+ push %gs
+ movl 36(%esp), %esi # esi <- RegSet
+ movzwl 0x32(%esi), %edx
+ mov 0xc(%esi), %edi
+ add $0xffffffc8, %edi
+ movl %edi, %ebx # ebx <- stack offset
+ imul $0x10, %edx, %eax
+ push $0xd
+ addl %eax, %edi # edi <- linear address of 16-bit stack
+ pop %ecx
+ rep
+ movsl # copy RegSet
+ movl 40(%esp), %eax # eax <- address of transition code
+ movl %edx, %esi # esi <- 16-bit stack segment
+ lea 0x5e(%eax), %edx
+ movl %eax, %ecx
+ andl $0xf, %ecx
+ shll $12, %eax
+ lea 0x6(%ecx), %ecx
+ movw %cx, %ax
+ stosl # [edi] <- return address of user code
+ sgdtl 0xffffffa2(%edx)
+ sidtl 0x24(%esp)
+ movl %cr0, %eax
+ movl %eax, (%edx) # save CR0 in SavedCr0
+ andl $0x7ffffffe, %eax # clear PE, PG bits
+ movl %cr4, %ebp
+ mov %ebp, 0xfffffff1(%edx)
+ andl $0x300, %ebp # clear all but PCE and OSFXSR bits
+ pushl $0x10
+ pop %ecx # ecx <- selector for data segments
+ lgdtl 0x20(%edx)
+ pushfl
+ lcall *0x14(%edx)
+ popfl
+ lidtl 0x24(%esp)
+ lea 0xffffffcc(%ebp), %eax
+ pop %gs
+ pop %fs
+ pop %es
+ pop %ds
+ pop %edi
+ pop %esi
+ pop %ebx
+ pop %ebp
+ ret
+
+ .const:
+
+ASM_PFX(m16Size): .word _InternalAsmThunk16 - ASM_PFX(m16Start)
+ASM_PFX(mThunk16Attr): .word _ThunkAttr - ASM_PFX(m16Start)
+ASM_PFX(m16Gdt): .word _NullSegDesc - ASM_PFX(m16Start)
+ASM_PFX(m16GdtrBase): .word _16GdtrBase - ASM_PFX(m16Start)
+ASM_PFX(mTransition): .word _EntryPoint - ASM_PFX(m16Start)
|